It has become the most natural thing to do: get in the car, type a destination into a smartphone, and let an algorithm using GPS data show the way. Personal GPS-equipped devices entered the mass market in only the past 15 or so years, but hundreds of millions of people now rarely travel without them. These gadgets are extremely powerful, allowing people to know their location at all times, to explore unknown places and to avoid getting lost.

But they also affect perception and judgment. When people are told which way to turn, it relieves them of the need to create their own routes and remember them. They pay less attention to their surroundings. And neuroscientists can now see that brain behavior changes when people rely on turn-by-turn directions.